In a hydrogen atom, what color is the emission line observed when electrons drop from the fifth to the second energy level?

Iknow #2 is d. i just need to know why

What does a particular point on a line of a phase diagram represent? o a. the maximum temperature a substance can exist at without bonds breaking b. the pressure created by the kinetic energy of molecules at a particular temperature c. the melting point or boiling point of a substance at a specific pressure d. the conditions in which temperature and pressure have equal effects on a substance

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '